Re: Singletons

Christoph Boget wrote:

Ok, so why isn't this working as (I, at the very least) expected? class singleTon {

    private static $thisObj = NULL;
    private $thisProp = NULL;

    public function __construct()
    {

echo 'singleTon::__construct()<br>';

      if( !is_null( singleTon::$thisObj ))
      {

echo '$thisObj already set. returning it...<br>';

        return singleTon::$thisObj;
      }
      singleTon::$thisObj = $this;
    }

    public static function singleton()
    {

echo 'singleTon::singleton()<br>';

      if( is_null( singleTon::$thisObj ))
      {
        $retval = new singleTon();
      }
      return singleTon::$thisObj;

    }

    public function setThisProp( $sVal )
    {
      $this->thisProp = $sVal;
    }

    public function getThisProp()
    {
      return $this->thisProp;
    }

} $one = singleTon::singleton(); $one->setThisProp( 'Joe' ); echo '$one->getThisProp();: [' . $one->getThisProp() . ']<br>'; echo '$one: [<pre>' . var_export( $one, TRUE ) . '</pre>]<br>'; $two = new singleTon(); echo '$two->getThisProp();: [' . $two->getThisProp() . ']<br>'; $two->setThisProp( 'Bob' ); echo '$two: [<pre>' . var_export( $two, TRUE ) . '</pre>]<br>'; echo '$one->getThisProp();: [' . $one->getThisProp() . ']<br>'; echo '$two->getThisProp();: [' . $two->getThisProp() . ']<br>'; echo '$one->getThisProp();: [' . $one->getThisProp() . ']<br>'; I would have thought that both $one and $two would be referencing the same object but they aren't. Apart from making the constructor private, is there any way I can ensure that there is ever only one instance of an object? thnx, Christoph

you can't return from a constructor; thus always use the static singleton method() i.e.: $two = singleTon::singleton(); -- nathan ( nathan@kraya.co.uk ) { Senior Web Developer php + java + flex + xmpp + xml + ecmascript web development edinburgh | http://kraya.co.uk/ }